Heart failure has previously been thought to be due exclusively to poor contractility of ventricles. More recently it has come to be understood that diastolic dysfunction can be a significant factor in heart failure. Diastolic dysfunction is believed to account for as many as 40% of all cases of congestive heart failure (CHF). One indicator of diastolic dysfunction is the time during which the left ventricular muscle relaxes following a contraction. The portion of the cardiac cycle between the end of left ventricle ejection and the opening of the mitral valve is known as the left ventricle isovolumetric relaxation time (LVIVRT). During this time, the left ventricle chamber size is not changing, as the left ventricle is neither emptying nor filling, but there is a change in pressure as the left ventricle relaxes. Another measure of diastolic dysfunction is the rate of filling of the left ventricle.
Measurement of diastolic dysfunction can be performed using invasive techniques, but there are significant risks to the patient. One such prior art technique uses a pressure sensing catheter inserted into the left ventricle via the pulmonary artery. However, the risks to the patient from using the pulmonary artery catheter preclude routine use. Alternatively, heart chamber function can be measured using echocardiograpy, which is safer than pulmonary catheterization and can be used either transthoracically or by esophageal echocardiography. However, echocardiography is difficult to perform, less accurate, and impractical to use for longer than a few minutes at a time. Consequently, it is difficult to obtain an accurate evaluation of the heart using esophageal echocardiography. Thus, there is a need for a less expensive, faster, and safer (in comparison to ventricular catheterization) method that can be used repetitively in a doctor's office, emergency room, operating room, or hospital setting.